Here's a place where I can post my thoughts on new papers, provide updates on my projects, and post info that will eventually be on my website The Theropod Database - http://theropoddatabase.com/ . It will center on theropods, but may delve into other topics as well such as phylogenetics.

Saturday, April 3, 2010

Pickering's taxa 2: Metriacanthosaurus brevis

Part 2 of Pickering's taxa. The comments on all these are going to have a similar section of course, since they all involve the same collection of Pickering manuscripts.

Comments- Owen (1857) originally described Megalosaurus ilia as coracoids, noting three specimens were in the BMNH and figuring one. Lydekker (1888) recognized these as ilia and incorrectly listed the one illustrated by Owen as BMNH 31811, though Pickering (DML, 2002) notes it is actually BMNH R1100. BMNH 31811 remained as a specimen of Megalosaurus bucklandii until Pickering credited the name Metriacanthosaurus brevis to English theropod material in his 1995 unpublished bibliographic manuscript. It was later used in the comparative section of another unpublished manuscript (Welles and Pickering, 1999). This paper was largely extracted from the European megalosaur manuscript Welles and Powell worked on in the 1970s but never published, specifically the Megalosaurus redescription section. Pickering intends to publish an updated version of the megalosaur manuscript as Mutanda Dinosaurologica, and has posted small excerpts including the diagnosis of Metriacanthosaurus "brevis" online (DML, 2002). In any case, the name is a nomen nudum as Pickering didn't follow ICZN Article 7 Recommendation 7a, Article 8a or Recommendation 8A. Pickering says of M. "brevis" and Metriacanthosaurus parkeri, "their great height and shortness -- diagnostic for Metriacanthosaurus -- separates them from ilia of Megalosaurus bucklandii and Allosaurus." Additionally, Allain and Chure (2002) stated BMNH 31811 and R1100 (misidentified as OUM J13560) are "quite different from one another in shape in proportions." However, Day and Barrett (2004) found the shortness was an illusion caused by a broken postacetabular process and a plaster reconstructed preacetabular process. Benson (2009) agreed and also found it shared an autapomorphy with other M. bucklandii ilia- a series of posterodorsally oriented ridges that give the posterior part of the median ridge an undulating texture. Indeed, the characters Pickering lists as distinguishing M. "brevis" from M. parkeri are largely also those that distinguish M. bucklandii from M. parkeri (nearly straight upper margin; taller preacetabular process), or don't distinguish M. "brevis" from M. bucklandii (narrower notch between preacetabular process and pubic peduncle; longer, lower acetabulum; 250 mm long). So I see no reason to support M. "brevis" and synonymize it with M. bucklandii.

Pickering also referred several other specimens to M. "brevis". OUM J29888 is a pectoral girdle which Day and Barrett and Benson couldn't distinguish from M. bucklandii. BMNH 31806 is a femur which Allain and Chure stated differs from the paralectotype in being straight with a medially directed head. Day and Barrett (2004) used this as the basis for their morphotype A femora, but Benson (2009) found the head orientation to be individual variation and the curvature of type B femora to be taphonomic. Additional differences between morphotype A and B femora were also found to be preservational or individual variation (see below), and Benson (2009, 2010) referred both types to M. bucklandii. Ironically, M.parkeri's femur has a sigmoid shaft, though it does have a medially directed head. BMNH 31809 and OUM J13562 are tibiae which Benson (2009, 2010) referred to M. bucklandii and which share a bulbous fibular crest with that taxon. BMNH 31809 differs from M. parkeri in having a smaller cnemial crest which is not as laterally angled and a smaller and more laterally placed fibular crest. Thus all supposed Metriacanthosaurus "brevis" material is referrable to Megalosaurus bucklandii and does not bear particular resemblence to Metriacanthosaurus itself. Coincidentally, BMNH 31806 and 31809 are the femur and tibia illustrated as examples of those elements in Benson's (2010) redescription of M. bucklandii, though the other tibia and the pectoral girdle remain unillustrated.

Day and Barrett, 2004. Material Referred to Megalosaurus (Dinosauria: Theropoda) from the Middle Jurassic of Stonesfield, Oxfordshire, England: one taxon or two? Proceedings of the Geologists' Association. 115, 359-366.
Galton and Molnar, 2005. Tibiae of small theropod dinosaurs from Southern England, from the Middle Jurassic of Stonesfield near Oxford and the Lower Cretaceous of the Isle of Wight: In Carpenter (ed). The Carnivorous Dinosaurs. 3-22.

Benson, 2009. An assessment of variability in theropod dinosaur remains from the Bathonian (Middle Jurassic) of Stonesfield and New Park Quarry, UK and taxonomic implications for Megalosaurus bucklandii and Iliosuchus incognitus. Palaeontology. 52(4), 857-877.

Benson, 2010. A description of Megalosaurus bucklandii (Dinosauria: Theropoda) from the Bathonian of the UK and the relationships of Middle Jurassic theropods. Zoological Journal of the Linnean Society. DOI 10.1111/j.1096-3642.2009.00569.x

In all seriousness, Olshevsky (one of the few people to actually have a copy) described it as follows-

"The book itself is a virtually exhaustive illustrated bibliography and filmography of the motion picture Jurassic Park, and it includes citations to numerous scientific dinosaur papers as well as, strangely enough, articles and other literature dealing with the Nazi Holocaust. It is difficult for me to see a common thread here, except perhaps that Steven Spielberg produced both Jurassic Park and Schindler's List motion pictures."

I shall not, of course, reply to the salacious, anti-intellectual, baiting analretentiveness expressed here. 'Qilong' and Mike Taylor are legends, alas, in their own minds...'Qilong', in particular, has no serious train of critical thought, so to speak, because serious ideas never occur to him, thus de-railing his avoidance of a colonic shower. I was raised, in part, by KZ 246744...this should humble 'Qilong' into retracting all of the above.I joke not.Kol tuv uv'racha.STEPHAN PICKERING / Chofetz Chayim ben-AvrahamTHE DINOSAUR FRACTALS PROJECT